Oscillating raceway grinder and method of grinding raceways



Jan. 18, 1949.

Filed June 26, 1946 W. D. ANDERSON OSGILLATING RACEWAY GRINDER AND METHOD OF GRINDING RACEWAYS 3 Sheets-Sheet 1 -52 "W16 IHHH In? K' WWII!! M Warm/2 fi, Andemom M A TTOR/VEY Jan. 18, 1949. w. D. ANDERSON 2,459,406

OSCILLATING RACEWAY GRINDER AND METHOD OF GRINDING RACEWAYS Filed June 26, 1946 3 SheetsSheet 2 m ATTORNEY Jan. 18, 1949. w. D. ANDERSON 2,459, 406

OSCILLATING RACEWAY GRINDER AND METHOD OF GRINDING RAGEWAYS Filed June 26, 1946 5 Sheets-Sheet 3 7; i 11. If

Patented Jan. 18, 1949 OSCILLATING, RACEWAY: GRINDER; AND

METHOD OE GRINDING RACEWAYS Warren D. Anderson; Glenbrookg Comm assignor to. Norma-,Hofixhann Bearings Corporation, Stamford: 0.0mm; all-corporation ofewwYorlc Application June 20-, 1946, Serial No. 679,400:

This invention relates tc oscillating; grindersof the type used for grinding the racewayswot anti-friction bearings and to amethod-for grinde ing said raceways.

The object of thisinventionis. to provide an improved apparatuscfor, andlmethod :01; grind ing very accurate raceway contours. Raceway. contour is defined as. the. curve; of intersection between the raceway'surface and-"alcuttingwplane defined by the parallelwaxes: oithe wheel spindle: and .the work spindle. wheelncontoui'yis defined; as the curve of. intersectionaof the wheel. perip'ha ery; adjacent. to the workpiece; with-.thellabove: plane. Center of oscillation: is defined 315i} the: point where the axis of oscillation intersects the: above plane;

The usual method of grinding ballbearingiracer ways on oscillating grinders: constructed accord:- ing tothe prior. artconsists-of mounting thel workpiece on. a workhead which. rotates: the; workpiece, about its: central :axis; ,and-oalso 059mmlates h the workpiece-about. an axis passing thruthe; center of curvature. of the raceway and; simultaneously subjecting. the raceway; to-.the.= action of a grinding wheel. As thermaterlalflofl the raceway is. ground away, the grindinguwheel is fed continuously into theiworkpiece until the raceway is of the desired. diameter. and..radius. of curvature. whenv the feeding. action. ,is stopped The grinding wheel isthen retractediromthe raceway and the workpiece. removed, from .the machine. A newworkpiece is then mounted ,in the machine and the wheelis again fed .towards the workpiece as previously described...

During the period when grinding is taking place, the oscillation .of the raceway in contact with the wheel tends to dress the wheelfcoyav circular contour, and also the, wheeltends to grind the raceway to a circular contour. Ideally, the raceway contour should be atrue circular "arcs when the grinding of the raceway is finished. Actually; however, i't'has been'found-in practice that raceways ground in this manner frequently deviate from a true circular are by an amount sumcient to seriously-impair'the operation of a precision ball bearingin which the radius of curvature of the1'aceway contour'isonly a-- few percent greater than the radius or the ball with theraceway.

Onthe basis of research; Ihavefound that m oscillating grinderscon-structed according to" theprior art; there is -afactor in th'e basic geomet rical & relationship -of the=- raceway; the grin-ding wheelandthe centerof oscillation; which-tends= to cause l the previously mentionederrors raceway contour. l

This invention consists of anoscillating grinder I in which b'oth the-'workiiead and-Wheelhead m'ay be given' feeding= movements relative to the-axis of oscillation; said-feeding movements being-providedto facilitatethe grinding of very-" accurate raceway con-tours.

Variousembodiments of this invention,- and combination of parts; will be-described herein after.

The-invention-also consists-in the method-oi 1 is a front elevationand" partial section- Fig. 2 is a plan view the -invention;

Fig; B'isa wiringdiagram -for-" the grinder;

of a grinder embodying Figs. 4-; 5 and S are enlarged plan views of the workpiece and' aportion ofthe grindingwheel showing the grinding" geometry =fo'r the usual grinder-constructed in" accordance with theprior art.

Figs. "7; 8 and 9am enlarged-plan views-cfthe workpiece -andav portion ofthe grinding wheel showing the grind-ing'geometry foran improved" grinder constructed in accordance with this in vention:

Similar characters of reference indicate cor at'th'e completion of grinding in an oscillating grinder, constructed "according to i the prior: art: It will be assumed that as the "result of diamond the workpiece from the grinder.

dressing or other special manipulation, both wheel contour I3 and finished raceway contour M are true circular arcs having a common center of curvature I coincident with the center of oscillation II. Both contours are coincident and of radius I 8.

Let the wheel be withdrawn from the raceway and the work removed from the grinder. In Fig. 5 is shown a new workpiece I9 and wheel II as the grinding commences. The new workpiece I8 has a previously formed raceway of radius I8. The center of wheel and raceway curvatures I5 is no longer coincident with the center of oscillation II but has been withdrawn a distance 2i from the center of oscillation. Distance 2| This interference causes a rapid breakdown of ii.

the wheel surface in the localized region 24 and also results in rapid removal of metal from the raceway surface in region 24, thus destroying the originally circular wheel contour I3 and raceway contour 20. A similar interference also occurs when the workpiece I9 oscillates thru a clockwise angle from the position shown in Fig. 5. These interference effects occur during each cycle of the oscillation, and their cumulative effect is to cause the wheel contour to become non-circular .15.-

in shape. Actual experience and precise measurements of wheel contour have shown that the corrective action of the raceway oscillating in contact with the wheel, is frequently insufficient to bring the wheel contour back to a true circular shape with the result that the finished raceway contour is also non-circular.

I have discovered that the above described interference effects may be completely eliminated if the center of wheel curvature I5 is kept centered on the center of oscillation I1, and the work is then fed toward the center of oscillation. In Fig. 7, the relative position of wheel I I and workpiece I2 is shown at the completion of grinding in an oscillating grinder constructed in accordance with this invention. It is again assumed that wheel contour I3 and finished raceway contour I4 are true circular arcs having a common center of curvature I5 coincident with the center of oscillation I'I. radius I8.

Now, let the center of wheel curvature I5 remain centered on the center of oscillation I1, and withdraw the workpiece from the wheel and remove Fig. 8 shows a new workpiece I9 and wheel II as grinding commences. The new workpiece I9 has a previously formed raceway 20 of radius I8. The center of wheel curvature I5 is coincident with the center of oscillation I1. However, the workhead 26, Fig. 2, and workpiece I9 are located at a distance 2I from the position shown in Fig. 7. Again the distance 2| represents approximately the amount of stock which will be removed from the surface of raceway 20.

In Fig. 9, the workpiece I9 has been oscillated thru a counterclockwise angle 23 from the position shown in Fig. 8. This oscillation takes place about the center of oscillation II. However, it will be seen that there is now no localized inter- Both contours are coincident and of.

ference between raceway 20 and wheel contour I 3. Furthermore, during the entire grinding cycle, raceway 20 and wheel contour I3 maintain a truly circular shape.

Therefore an oscillating grinder constructed in accordance with this invention, eliminates one of the factors tending to cause non-circular raceway contours.

The preceding discussion has, for reasons of simplicity, not considered the eifect of wheel wear. It would be entirely possible to grind a number of rings without compensating for wheel wear, however, wheel wear would cause radius I8, Fig. 7, to become progressively smaller. In actual practice, however, it is desirable to maintain radius I8 at a fixed value, and thus it is desirable to provide for a feeding movement of wheel II towards center of oscillation I! to compensate for wheel wear.

Ideally, wheel II should be fed continuously towards center of oscillation I! at exactly the same rate that wheel surface I3, Fig. 9, wears away, and thus the center of wheel curvature I5 would at all times be precisely coincident with center of oscillation I1. Practically, however, the wheel wears very slowly and particularly for large diameter wheels and small diameter workpieces an intermittent feeding of the wheel towards the center of oscillation may be substituted for the ideal continuous feed. Such an intermittent wheel feed might take place during a portion of the grind.-

ing time ormight take place after one or more,

pieces had been ground, or might take place both during and after grinding. In any type of inter mittent wheel feed it is evident that after the feed has taken place, the center of wheel curvature I5 will be separated from the center of oscillation I! by a small distance equal to the amount of the wheel feed. Further, in" order to 3 minimize wheel and raceway interference effects,

the distance between the center of wheel curvature I5 and center of oscillation I! must be small relative to the total amount of stock removal corresponding to the distance 2 I. When the distance between the center of wheel curvature I5 and the center of oscillation I1 is small relative to the total amount of stock removal 2 I, the center of curvature I5 of the wheel contour will be defined as being substantially coincident with the center of oscillation [7.

Furthermore, this previous discussion has assumed that the raceway in the new workpiece III will always have-an accurate contour of radius I 8 and that this contour will always have its center.

of curvature at a common distance from the locating face of the ring. In actual practice this condition is frequently not realized since the raceway in the new workpiece I9 may be off center in one direction or the other, or may have a raceway contour which is not truly circular. For these and other reasons, it is evident that the initial contact'between the raceway in the new workpiece I9 and wheel contour I3 may not be precisely coincident as shown in Figs. 8, and 9. In such a case, during the initial grinding of raceway 20 the wheel will wear to a non-circular contour which has not one center of curvature but many centers. In such a case, we cannot correctly say that the wheel contour has a center of curvature coincident with the center of oscillation. However, we can avoid the interference effects shown in' region 24 of Fig. 6, if the distances between the center of oscillation I! and successive ri in po it ons. o the w e ax s. form an alascends...

5. ways decreasing sequence. In other words-penccessive grinding positions of the wheel axis. will alwaysbecloser to the center of oscillation ll than at any previous instant of time.

In grinders constructed according to the prior art, requirement is not met since the distance from thegrinding position of the wheel axis to the, center of oscillation is increased by: the. amount 2| each time that a new, workpiece is placed in the grinder, Grinding position oi; the axis defined as the position of th wheel axis at any time that r ndin is taking place, as, distinguished from a loading position of the wheel axis. with the wheel moved back from the oscillation, therefore, if successive raceways are to have accurate contours of a fixed radius, it is essential that the feeding motions of the wheel and work must occur in accurately repeated cycles. In order to minimize variations in radius [8 and in order to minimize the previously described interference effect, it is necessary that during the grinding action the variation in the distance between the axis of oscillation and the region where the grinding is taking place, should be small relative to the total amount of stock removal representedby distance 2|. In such a case the grinding action will be defined as occurring at a substantially fixed distance from the axis of oscillation.

The underlying concept of the improved method is then the subjection of the raceway to a-grind ing action at a substantially fixed distance from the axis of oscillation, in accurately repeated cycles, during which cycles the raceway is simultaneously rotated about its central axis and oscillated about a non-parallel axis.

To one skilled in the art, it will be evident that thisin-vention may be embodied in various types of raceway grinders. Various methods of effecting and coordinating the feeding motions of the workpiece and wheel relative to the center of oscillation could be employed. For purposes of description. an embodiment of this invention is shown in Figs. 1, 2, and 3. The grinder shown has many features known to the prior art, and for reasons ofsimplicity, only those parts have been shown which are necessary for the description of the present invention.

Referring to Figs. 1 and 2, workpiece I9 is mounted on work spindle which is mounted in suitable bearings in workhead 26, and is belt driven by work drive motor 21 which is fastened to workhead 26. Workhead 2B is laterally adjustable a-long dovetail ways 28'and may beclamped in. position by screw clamp 29. Ways 28 are integral with. work slide 30 which may be given a fore. and aft feeding motion along dovetail ways 3| whichare integral with. oscillating table 32. Table 32 is supported by suitable bearings 33 and 34 to permit oscillation about the axis ll-.-.-ll. The feeding motion of work slide 39 along ways 3| is effected by feed screw 35. which.

(i has one end threaded into. work slide 3.0, and the other end positioned by a suitable thrust,

bearing in gear box 36, which is fastened to.

oscillating table 32' by screws 36a; Gear box 3.6 contains suitable reduction gears connecting the,- reversible, variable speed, work; feed motor 31. to feed screw 35,, as known and not shown.

Fastened to table- 3.2 is a single pole, double throw limit switch38, which is actuated on for-. wardmovement of work slide 30 by adjustable screw 39. Double pole, double throw limit. switch 42 is fastened to table 32 and is actuated on reverse movement of work slide 30 by adjustable screw 43.

The oscillation of table 32 about axis 11,-, Fig. 1, is effected by lever 44, connecting rod 45 and eccentric 46, which is mounted on gear box 61, and is connected by suitable gears to oscillating. drive motor 48, gear box 41 being fastened to base 49. shown in detail.

Grinding wheel {I is mounted on spindle 5.9 which is. supported by suitable bearings in wheel head 5| and is belt driven by wheel drive motor 52 which is preferably mounted on Wheel head 5|. Wheel head 5| is laterally adjustable on dovetail ways 53 and may be clamped in position by screw clamp 54, Ways 53 are integral with wheel slide 55. Wheel slide 55 may be given a fore and aft feeding motion along dovetail ways 56 which are integral with base 99. The feeding motion of wheel slide 55 along ways 55 is eifected by feed screw 51, which has one end threaded into wheel slid 55, and the other end positioned by a suitable thrust bearing in gear box 58. Gear box 58 is fastened to base 59 by screws or bolts 58a, and contains suitable reduction gears connecting feed screw 51 to the reversible, variable speed, wheel feed motor 59, known and not shown in detail. s

The coordination of the various drive motors is accomplished by suitable electrical control cir-. cuits, as shown in the wiring diagram, Fig. 3. By suitably changing the control circuit, there are six distinct control cycles coordinating the feeding motions of workhead 26 and wheelhead 51. relative to the center of oscillation ll.

As a first type of coordinated control, consider the operation. of the grinder with the control cira cuit arranged to provide automatic coordinated feed, and withdrawal of workpiece l9 relative to the center of oscillation IT, and. concurrent feeding motion of wheel H towards the center of.

oscillation I1. Referring to the wiring diagram, Fig. 3, a suitable source of electric power is pros vided to impress a voltage as indicated in Fig.

3. Let single-pole, double throw reversing switch 12 contact terminal 92 thus energizing the for. ward field of wheel feed motor 59, the M meaning motor in Fig; 3. Let switches 59, GI, 94, 95, 88 and 86 be closed and let switches 91 and 89 be open. Furthermore, let work slide 30 be in re tracted position so that screw 43 holds doublepole, double throw, limit switch 42 in position to leave contacts Hand M open.

With workpiece I9 in position, the operator starts the cycle by closingnorinally open momen tary contact switch 62 thus energizing winding 63. of triple. pole, double throw magnetic relay 64, thus liftingtherelay armature and contact pieces 64a, and thus connecting contacts 65 to 66, 98 to 69 and 19 to H. These connections. provide a holding circuit thru winding 63, start work feed motor 31 in a forward direction tofeed workpiece l9 towards. center of oscillation H, and

These parts ar known and not start wheel feed motor 59 in a forward direction.

to feed wheel ii toward center of oscillation ll. As work slide Cit moves forward, screw 43 moves away from limit switch 42, thus completing circuits thru normally closed contacts 13 and thus keeping motors 3i and 59 running, and starting oscillation drive motor 48 and work drive motor 21. The feeding motions of workpiece l9 and wheel i l toward center of oscillation ll continue during the grinding of raceway 20 until screw 39 actuates single-pole, double throw limit switch 38, and thus stops work feed motor and wheel feed motor 59, and also breaks the holding circuit thru winding 63 thus allowing the relay armature to drop out and connect contacts 75 to l6, 1'? to '18, and '19 to all. Also, limit switch 38 completes a circuit thru contact 8! and winding 82 of pneumatic time-lag relay 83 having normally open contacts 84 and 85. The interval required for relay 83 to close, allows the grinding wheel to spark-out. When relay 83 closes, it connects contacts 84 to 85, and thus provides a circuit thru contacts 15 to 76 to 13, and also pro vides another circuit thru contact ii to 78, thus causing work feed motor 3'! to run in a reverse direction and withdraw workpiece l9 away from center of oscillation ll. Also, a circuit is established between contacts '69 and 80, thus starting wheel feed motor 59 in a forward direction to provide further feed of wheel ll toward center of oscillation ll, while the workpiece is Withdrawing. The withdrawal movement of workpiece l9 continues until screw it? actuates limit switch 42, thus stopping motors 31, 59, 2i and 48. The workpiece I9 is then removed from the grinder, and the raceway diameter measured on a suitable measuring instrument. If the raceway diameter is too large, it indicates that the wheel feed is insuificient to compensate for wheel wear, and consequently it is necessary to increase the speed of wheel feed motor 59. Conversely, if the raceway diameter is too small, the speed of wheel feed motor 59 must be decreased. Thus, by trial and error, the speed of wheel feed motor 59 is adjusted so that the amount of wheel feed will just compensate for the amount of wheel wear, and thus for successive raceways the wheel contour i3 and raceway contour M will have a fixed value for radius 58.

As a second type of coordinated control, consider the operation of the grinder with the control circuit arranged to provide automatic coordinated feed and withdrawal movements of workpiece l9 relative to center of oscillation l1 and a feeding movement of wheel I! toward center of oscillation ii during the grinding period only. Consider the circuit arrangement to be identical with that previously described, except let switch 85 be open. The operation of the grinder will be identical with the first type of operation except that when relay 83 closes to reverse the work feed motor, there will be no circuit thru switch S6 and thus wheel feed motor 59 will not provide any feeding motion of wheel ll toward center of oscillation l1, while workpiece I9 is withdrawing from center of oscillation l'i. As previously described, it will be necessary to make a trial and error adjustment of the speed of the wheel feed motor 59 in orderthat the amount of wheel feed will just compensate for wheel wear.

As a third type of coordinated control, consider the operation of the grinder with the control circuit arranged to provide automatic coordinated feed and withdrawal movements of workpiece l9 relative to center of oscillation l1, and a feeding movement of wheel I l toward center of oscillation I! during the withdrawal period only. Consider the circuit arrangement to be similar to that used for the first type of control, except let switch 88 be open. The operation of the grinder will be identical with the first type of operation, except that when winding 63 or relay 64 is energized there is no circuit thru switch 88 and consequently while workpiece l9 feeds toward center of oscillation I1, there is no feeding movement of wheel I I toward center of oscillation H. However, as soon as relay 83 closes to reverse work feed motor 31 and withdraw Workpiece 19, wheel feed motor 59 will feed the wheel ll toward center of oscillation [7. Again, the speed of wheel feed motor 59 should be regulated to just compensate for wheel wear.

The above described completely automatic grinding cycles are frequently desirable, since they permit one operator to load and unload several grinding machines with a resultant economy in labor cost per piece ground. However, under certain conditions of operation, it may be desirable to provide a semi-automatic control of the grinding wheel feed in order to permit modification of the grinding cycle in accordance with visual observation as the raceway is being ground.

As a fourth type of coordinated control, consider the operation of the grinder with the control circuit arranged to provide automatic coordinated feed and withdrawal movements of workpiece 19 relative to center of oscillation l1. However, the feeding movements of wheel ll toward center of oscillation I! will be manually controlled and will be coordinated to occur during either feeding or withdrawal movements of the work. Consider the circuit arrangement to,-

be similar to that described for the first type of control, with the exception that switches 86 and 88 are open and switches 81 and 89 are closed. The operation of the grinder will be identical with that described for the first type of control, except that feeding movements of wheel ll do not take place automatically. While winding 63 is energized and workpiece I9 is feeding toward center of oscillation [1, wheel feed may be controlled manually by depressing the normally open momentary contact switch 9!. When workpiece I9 is withdrawing from center of oscillation H, the

feed of wheel ll towardcenter of oscillation I! may be manually controlled by depressing normally open momentary contact switch 90.

As a fifth type of coordinated control, consider operation of the grinder with the control circuit arranged to provide automatic coordinated feed and withdrawal movements of workpiece l9 relative to center of oscillation I1. However, the feed of wheel il toward center of oscillation I! will be manually controlled and coordinated to take place only while workpiece I9 is feeding toward axis of oscillation I1. Consider the circuit arrangement to be similar to that for the first type of control, except that switches 86, 88 and 81 are open and switch 89 is closed. The operation of the grinder is identical with the first type of operation, except that no automatic feeding movements of the wheel occur and manual control of the wheel feed is possible by depressing normally open momentary contact switch 9|, only while winding 63 is energized and workpiece i9 is feeding toward center of oscillation I1.

As -a sixth type of coordinated control, consider operation of the grinder with the controlcircuit arranged to provide automatic coordinated feed and withdrawal movementsof workpiece I9 relative to center of oscillation I1, and provision for a manually controlled feed of work H toward center of oscillation I! only during the period that workpiece i9 is withdrawing from center of oscillation ll. Consider the circuit arrangement tobe identical with that described for the first type of control, except that switches 86, 88 andBS are pressing normally open momentary contact switch 90 during the period that workpiece I9 is ,withdrawing from center of oscillation l1.

Although not directly concerned with the grinding operation, the circuit shown in Fig.3 iricorporates a number of supplementary switches for use in setting-up and adjusting the grinder. With single-pole, double throw reversing switch 12 in position to contact terminal 93, it is evident that closing of switch 86 will cause the wheel feed motor59;to reverse and thus withdraw wheel I I from center of oscillation ll to permit replacing a worn wheel with a new and larger wheel. Jogging movements of-work feed motor 31 and work slide 30 may be effected by opening switches 94 and =95 and actuating normally open momentary contact switches 96 and 9'! to cause forward and reverse jog movements respectively.

For reasons of clarity and brevity, this invention has been described with particular reference to the grinding of inner ring raceways for antifriction bearings. However, the basic relationship concerning the geometry ofthe grinding wheel contour, raceway contour and center of oscillation apply equally well in the grinding of raceways for outer rings of anti-friction bearings, and thereforethis invention applies to outer ring raceway grinders as well as inner ring raceway grinders.

Although the invention has been described in some detail with reference to a particular design of raceway grinder and a particular arrangement of control circuits, it is understood that this was done only by way of example, and that numerous changes in the details of construction and means -of coordinating the feeding movements of the wheel and work relative to the center of oscillation may be resorted to without departing from the spirit of the invention as hereinafter claimed. For example the feeding and withdrawal movements of the workhead and wheelhead might be effected by pneumatic, hydraulic, or mechanical mechanism. Also, the feeding movement of the wheel toward the center of oscillation might be controlled by a suitable control circuit actuated by an automatic sizing device or switch responsive to the diameter of the raceway being ground, Numerous other modifications will be evident to one skilled in the art.

I have described several forms of my invention, but obviously various changes may be made in the details disclosed without departingfrom the spirit of the invention as set out in the following claims.

I claim:

1. In an oscillating raceway grinder having a workhead rotating a workpiece, a wheelhead rotating a grinding wheel, and a power driven mechanism for oscillating the workpiece about anaxis of oscillation, the combination of a power driven mechanism for feeding the workpiece relative to the axis of oscillation, :a mechanism for feeding the wheel relative to the axis of oscillation, and a control mechanism integral with the grinder for coordinating said feed mechanisms. '2. In an oscillating raceway grinder having a workhead rotating a workpiece, a wheelhead ro- -tating -a grinding wheel, and a power driven mechanism for oscillating the workpiece about an axis of oscillation, the combination of a power driven mechanism for feeding the workpiece relative to the axis of oscillation, a mechanism for feeding the wheel relative .to the axis of oscillation, and a control means integra] with the grinder for coordinating said feeding mechanisms to make the distances between the oscillation axis and successive grinding positions of the wheel axis form an always decreasing sequence.

3. In an oscillating raceway grinder having a workhead rotating a workpiece, a wheelhead rotating a grinding wheel, and a power driven mechanism for oscillating the workpiece about an axis of oscillation, the combination of a Power driven mechanism for feeding the workpiece relative to the axis of oscillation, a mechanism for feeding the wheel relative to the axis of oscillation, and a control means integral with the grinder for coordinating said feed mechanisms to keep the center of curvature of the wheel contour substantially coincidentwith the oscillation axis while the workpiece is being ground.

4. In an oscillating raceway grinder having a workhead rotating a workpiecaa wheelhead rotating a grinding wheel, and a power driven mechanism for oscillating the workpiece about an axis of oscillatiomthe combination of a power driven mechanism for feeding the workpiece relative to the axis of oscillation, and a mechanism, operative only while'grinding is taking place, for feeding the wheel relative tothe axis of oscillation.

"5. 'In an oscillating raceway grinder having a workhead rotating a workpiece, a wheelhead rotating a grinding wheel, and a power driven mechanism for oscillating the workpiece about an axis of oscillatiomthe combination of a power driven mechanism for-feedingthe workpiece relative to the axis of. oscillation, a mechanism, operative only while'grindingis taking place, for feeding the wheel relative to the axis of oscillation, and a control means for coordinating said feed mechanisms .to make the distances between the oscillation axis and successive positions of the wheel axis form an always decreasing sequence.

6. In ,an oscillating raceway grinder having a workhead rotating .a workpiece, a wheelhead rotating a griding wheel, and a power driven mechanism for oscillating the workpiece about an axisor oscillation, the combination of a power driven mechanism for feeding the workpiece relative to the axis, of oscillation, ,a, mechanism,

operative only while grinding is taking place, for

s o pscil atioa t e comb nati n ofapow driven mechanism for feeding the workpiece rel- 11 ative to the axis of oscillation, and a mechanism, operative only after grinding has been completed, for feeding the wheel relative to the axis of oscillation.

8. In an oscillating raceway grinder having a workhead rotating a workpiece, a wheelhead rotating a grinding wheel, and a power driven mechanism for oscillating the workpiece about an axis of oscillation, the combination of a power driven mechanism for feeding the workpiece relative to the axis of oscillation, a mechanism, operative only after grinding has been completed, for feeding the wheel relative to the axis of oscillation, and a control means for coordinating said feeding mechanisms to make the distances between the oscillation axis and successive grinding positions of the wheel axis form an always decreasing sequence.

9. In an oscillating raceway grinder having a workhead rotating a workpiece, a wheelhead rotating a grinding wheel, and a power driven mechanism for oscillating the workpiece about an axis of oscillation, the combination of a power driven mechanism for feeding the workpiece relative to the axis of oscillation, a mechanism, operative only after grinding has been completed, for feeding the wheel relative to the axis of oscillation, and a control means for coordinating said feeding mechanisms to keep the center of curvature of the wheel contour substantially coincident with :the oscillation axis while the workpiece is being ground.

10. In an oscillating raceway grinder having a workhead rotating a workpiece, a wheelhead rotating a grinding wheel, and a power driven mechanism for oscillating the workpiece about an axis of oscillation, the combination of a power driven mechanism for feeding the workpiece relative to the axis of oscillation, and a power driven mechanism for feeding the wheel relative to the axis of oscillation.

11. In an oscillating raceway grinder having a workhead rotating a workpiece, a wheelhead rotating a grinding wheel, and a power driven mechanism for oscillating th workpiece about an axis of oscillation, the combination of a power driven mechanism for feeding the workpiece relative to the axis of oscillation, a power driven mechanism for feeding the wheel relative to the axis of oscillation, and a control means for cordinating said feeding mechanisms to make the distances between the oscillation axis and successive grinding positions of the wheel axis form an always decreasing sequence.

12. In an oscillating raceway grinder having a workhead rotating a workpiece, a wheelhead rotating a grinding wheel, and a power driven mechanism for oscillating the workpiece about an axis of oscillation, the combination of a power driven mechanism for feeding the workpiece relative to the axis of oscillation, a power driven mechanism for feeding the wheel relative to the ing place, for feeding the wheel relative to the axis of oscillation.

14. In an oscillating raceway grinder having a workhead rotating a workpiece, a wheelhead rotating a grinding wheel, and a power driven mechanism for oscillating the workpiece about an axis of oscillation, the combination of a power driven mechanism for feeding the workpiece relative to the axis :of oscillation, a power driven mechanism, operative only while grinding is taking place, for feeding the wheel relative to the axis of oscillation, and a control means for coordinating said feeding mechanisms to make the distances between the oscillation axis and successive grinding positions of the wheel axis form an always decreasing sequence.

15. In an oscillating raceway grinder having a workhead rotating a workpiece, a wheelhead rotating a grinding wheel, and a power driven mechanism for oscillating the workpiece about an axis of oscillation, the combination of apower driven mechanism for feeding the workpiece relative to the axis of oscillation, a power driven mechanism, operative only while grinding is taking place, for feeding the wheel relative to the axis of oscillation, and a control means for coordinating said feeding mechanisms to keep the center of curvature of the wheel contour substantially coincident with the oscillation axis while the workpiece is being ground.

16. In an oscillating raceway grinder having a wo'rkhead'rotating a workpiece, a wheelhead rotating a grinding wheel, and a power driven mechanism for oscillating the workpiece about an axis of oscillation, the combination of a power driven mechanism for feeding the workpiece relative to the axis of oscillation, and a power driven mechanism, operative only after grinding has been completed, for feeding the wheel relative to the axis of oscillation.

17. In an Oscillating raceway grinder having a workhead rotating a workpiece, a wheelhead rotating a grinding wheel, and a power driven mechanism for oscillating the workpiece about an axis of oscillation, the combination of a power driven mechanism for feeding the workpiece relative to the axis of oscillation, a power driven mechanism, operative only after grinding has been completed, for feeding the wheel relative to the axis of oscillation, and a control means for coordinating said feeding mechanisms to make the distances between the oscillation axis and successive grinding positions of the wheel axis form an always decreasing sequence.

18. In an oscillating raceway grinder having a workhead rotating a workpiece, a wheelhead rotating a grinding wheel, and a power driven mechanism for oscillating the workpiece about an axis of oscillation, the combination of a power driven mechanism for feeding the workpiece relative to the axis of oscillation, a power driven mechanism, operative only after grinding has been completed, for feeding the wheel relative to the axis of oscillation, and a control means for coordinating said feeding mechanisms to keep the center of curvature of the wheel contour substantially coincident with the oscillation axis while the workpiece is being ground.

19. In an oscillating raceway grinder in which an anti-friction bearing raceway is simultaneously rotated about its central axis, oscillated about a non-parallel axis, and subjected to the action of a grinding wheel, the combination of means giving the raceway a feeding motion towards the axis of oscillation, means giving the grinding wheel a feeding motion towards the axis of oscillation, and means simultaneously regulating both the raceway and the grinding wheel feeding motions proportional to the respective rates of wear of the raceway and grinding wheel, so that the grinding action occurs at a substantially fixed distance from the axis of oscillation. v

20. The method of grinding anti-friction bearing raceways during which the raceway is simultaneously rotated about its central axis, oscillated about a non-parallel axis, and subjected to the action of a grinding wheel, which consists in subjecting the raceway to the grinding action at a substantially fixed distance from the axis of oscillation, and subjecting under positive control the raceway and the grinding wheel each to a movement towards the axis of oscillation propor- REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,286,977 Fenaux Dec. 10, 1918 1,306,400 Barr June 10, 1919 2,149,409 Van Norman et a1, Mar. 7, 1939 

